Automated sequential gas sampling system

ABSTRACT

A gas sampling system includes a sample trapping module having a gas pump and a power supply, and a removable magazine that fits within a port of the trapping module. The magazine contains a non-volatile electronic memory, which controls operation of the trapping module, and has a rotating carousel for holding sample tubes. Individual sample tubes are sealed at each end by a cap that has a needle-pierceable septum, and contain a solid collector material to trap chemical and biological contaminants in a gas sample drawn through the sample tube. Individual sample tubes are moved into and out of a sampling location by incremental rotation of the carousel and, while at the sampling location, a pair of hollow bore needles are inserted through the sample tube end caps to allow the drawing of a gas sample through the tube.

FIELD OF THE INVENTION

This invention relates generally to sampling devices for determining thenature and quantity of chemical and biological contaminants in air andother gases.

More specifically, this invention concerns a gas sampling system thatincludes a sample trapping module, a magazine holding a plurality ofcollector-filled sampling tubes, a control that operates the trappingmodule, and an interface to analytical instruments.

DESCRIPTION OF RELATED ART

There is a large and continuing need for identifying and monitoring thelevel of pollutants in air and in industrial gas streams. In the pastthis task was usually performed by obtaining a sample of the air at themonitoring site, and transporting that sample to a laboratory foranalysis. Samples were ordinarily obtained by manually filling asampling container, such as a plastic bag, a hypodermic syringe, or anevacuated metal or glass vessel, and sealing it for transport.

That approach was very expensive, particularly in terms of the personnelneeded for periodically taking samples over a long time interval.Consequently, there was developed a number of sampling devices forcollecting air samples at predetermined intervals over an extended timeperiod. One such device is shown in the Griffith patent, U.S. Pat. No.3,884,081. The Griffith sampler uses a plurality of piston pumps thatmay be hypodermic syringes of appropriate capacity. The plunger of eachpump is retracted by mechanical means at a scheduled time to draw an airsample into the pump barrel.

Another sampler that operates in the same general fashion is disclosedin U.S. Pat. No. 3,540,261, to Scoggins. Scoggins provides a magazinecontaining a number of individual sample containers. The magazine ispowered by a time controlled drive system that sequentially indexes thesample containers into registry with a monitoring station where eachcontainer is connected with a vacuum source that draws a gas samplethrough the container, and stores the sample for further processing.

Sampling devices that take a bulk air sample for transport and lateranalysis are often inappropriate for use in those circumstances in whichthe contaminant being monitored is present in small concentration, inthe parts per million or even parts per billion range. The size of thesample that is collected is often too small for the contaminant to bedetected and its concentration measured. That requirement has led to thedevelopment of sampling devices which employ sample containers thatpreferentially extract a contaminant from the sampled gas stream, andhold the trapped contaminant for later release and analysis.

Two patents illustrate that approach to sampling. The first is a patentto Galen, U.S. Pat. No. 4,584,887, which discloses a sampling systemhaving a sample module that may be detached from a flow assembly module.The sample module includes a plurality of small parallel tubes arrangedlongitudinally about the periphery of a circular frame. Each tubecontains a sorbent material that functions to extract and holdcontaminants from an air stream passing through the tube. Because mostcontaminants of interest are organic compounds, the sorbent material ischosen to adsorb those compounds while allowing inorganic compounds topass through the tube substantially unimpeded. In use, the sample moduleis mated with the flow assembly module, and sample tubes aresequentially indexed to and connected in series with the sampler inletand exhaust ports of the flow assembly module by means of a selectorvalve. A predetermined volume of air is then pumped through the indexedsample tube, and the airborne contaminants are trapped on the sorbentmaterial.

The second patent of interest here is U.S. Pat. No. 4,869,117 thatissued to McAndless et al. Like Galen, the McAndless patent uses acylindrical sample magazine which holds a plurality of small sampletubes that are packed with a solid adsorbent. The sample tubes aresymmetrically arranged in a circle about the longitudinal axis of themagazine. The McAndless device differs from that of Galen in that theindividual sample tubes are not isolated from each other by way of valvemeans. Instead, McAndless et al provide a sampling inlet and outletextending through the magazine housing at a sampling position.Individual tubes are sequentially advanced to and then from the samplingposition. While at the sampling position, both ends of the sample tubeare sealed so that the tube is positioned in series between the samplesource and an air pump which draws an air sample through the tube.

Finally, Lawrence in a paper published in the Journal of Chromatography,395 (1987) 531-538, Elsevier Science Publishers, describes an interfacefor transferring high boiling compounds from a sample adsorption tube tothe column of a gas chromatograph for analysis. The sample tubesdescribed and illustrated by Lawrence are generally similar to thoseused by McAndless et al.

Despite the developments in sampling techniques described in the priorart, there still exists a need for systems that can obtain a largenumber of samples at remote and unattended locations, and maintain theintegrity of each sample taken until analysis is complete. The system ofthis invention fills that need.

SUMMARY OF THE INVENTION

The sampling system of this invention includes a sample trapping module,a magazine, sample tubes, and an interface means that functions toenable cooperation between the magazine, the sample tubes and ananalytical instrument. The sample trapping module is arranged to holdthe magazine during sampling, to sequentially index sample tubes intoand out of sampling position within the magazine, to monitor samplingconditions and to collate that data with each individual sample, and toaccept: control instructions from non-volatile memory carried in themagazine. In turn, the magazine houses a plurality of individualsampling tubes and contains memory means adapted to control operation ofthe trapping module and to accept and preserve data relating to thesamples that are taken by the sample trapping module. Sample tubes usedin the invention consist of elongated, sealed tubes which contain asolid collector material that can selectively remove a chemical orbiological contaminant of interest from a gas stream that is passedthrough the tube. Lastly, the interface means is arranged to facilitatethe removal of sample tubes from the magazine, and to releasecontaminants from the collector material contained within the samplingtubes for analysis using conventional procedures.

Hence, it is an object of this invention to provide an unattended,integrated sampling system for repeatedly sampling a gas or air streamat predetermined times to concentrate and collect chemical andbiological contaminants for later analysis.

It is a further object of this invention to provide a novel samplingmagazine that is arranged to house a plurality of sampling tubes, andwhich contains non-volatile memory that controls the sampling processand stores data relating to the sample taken by each individual samplingtube.

Yet another object of this invention is to provide a novel sampling tubefor use in the sampling system.

Other objects of this invention will be evident from the followingdetailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view of the major elements of the sampling system,showing how the elements interact;

FIG. 2 is a partial sectional view of a sample tube that is used withthe sampling system of this invention;

FIG. 3 is a cross-sectional view of a sample tube end closure;

FIG. 4 is a front view of the sample trapping module showing itsoperating parts;

FIG. 5 is a an end view of the needle drive mechanism of the sampletrapping module of FIG. 4;

FIG. 6 is a bottom, internal view of the sampler magazine;

FIG. 7 is a front view of the sampler magazine showing its internalconstruction;

FIG. 8 is a view of the sampler magazine encoder plate that signals therotational position of the magazine;

FIG. 9 is a top view of the magazine carousel drive mechanism of thesample trapping module;

FIG. 10 is a side view of the drive mechanism of FIG. 8;

FIG. 11 is a bottom view of the drive mechanism of FIG. 8;

FIG. 12 is a schematic depicting the operational control of the samplingprocess;

FIG. 13 is an expanded schematic diagram of the memory and controlarrangement shown in FIG. 12, and

FIG. 14 is a schematic depiction of a system for the analysis of samplescaptured in the sample tubes of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 schematically depicts the major elements of the sampling system10 and the relationship of those elements one to another. System 10includes a sample trapping module 12, a magazine 14, a plurality ofsample tubes 16, and an interface means 18. The first three majorelements, the trapping module, magazine, and sample tubes, constitutethe field portion of the system while interface means 18 in cooperationwith desorber 270 is used at an analytical laboratory to operablyinterconnect the magazine to an analytical instrument.

In operation, magazine 14 is first loaded with sample tubes 16 and thefilled magazine is inserted into port 20 of the trapping module 12 toready the field portion of the system for sampling. The system fieldportion is taken to a sampling location, and samples of the atmosphereat the sampling location are obtained by drawing a predetermined volumeof gas through individual sample tubes.

The sample tube design is a critical feature of the sampling system ofthis invention as it facilitates the automation of the entire samplecollection and analysis process. While samplers which use so-called“minitubes” are finding increasing acceptance, there has not yetdeveloped an industry standard for physical dimensions and mechanicalconfiguration of such tubes. Nevertheless, it is preferred that thesample tubes used in the sampling system of this invention conform tothe physical dimensions of those sample tubes that are compatible withthe automatic thermal desorption unit which is manufactured by PerkinElmer Corporation as that system controls a large share of the relevantcommercial market. Those particular sample tubes comprise an elongatedtube having a removable cap at each end. The tubes are manufactured ofstainless steel, glass, or glass lined stainless steel having an outsidediameter of 0.250″, a bore of 0.190″, and a length of 3.50″.

Referring now to FIGS. 2 and 3, there is illustrated a preferredstructure of the sample tubes that are used in the inventive system.Referring first to FIG. 2, sample tube 16 is shown in partial crosssection and includes a tube body 30 and a pair of end caps 31. The endcaps are preferably manufactured from a chemically inert material whichsuitably may be a polytetrafluoroethylene polymer such as Teflon®, anduse an O-ring to form a seal between the cap bore and the outer surfaceof the sample tube. Tube body 30 and end caps 31 preferably conform inphysical dimensions to those sorbent tubes and caps used in the PerkinElmer automatic thermal desorber system. The central portion of the tubebore is filled with a collector material 33, 34, 35 that is selected toremove specific contaminants from the gas stream being sampled. Thecollector material is held in place within the tube bore by means ofporous plugs 37 of glass wool or similar material. It must be arrangedto allow reasonably free flow of gas through the tube during thesampling process while at the same time ensuring thorough and extendedcontact between the gas and the collector material. The collectormaterial is ordinarily employed in particulate form, and a size range of20/60 mesh is usually appropriate.

Composition of the collector material is tailored to the specific suiteof contaminants that is being monitored. In many instances, thecomposition of collector materials 33, 34 and 35 are different one fromanother, especially in those circumstances wherein the presence andconcentration of a variety of different contaminants is being monitored.In other instances, the composition of collector materials 33, 34 and 35may be the same, especially if only one, or one type of contaminant, isto be monitored. For example, if a user is monitoring ambient air forchemical contaminants having a range of activities or molecular weights,then the use of several different adsorbents as collector materials inthe same sample tube results in obtaining more complete andrepresentative samples. On the other hand if a specific contaminant isbeing monitored, then use of a collector material that is tailored toadsorbing and trapping that particular contaminant offers advantages. Insome circumstances, particularly when the composition of collectormaterials 33, 34 and 35 differs, it is important to fix the direction ofgas flow through the sample tube. In order to obtain that result, thereis provided orienting indicia that may be one or more orienting grooves39 about the exterior of tube body 30, adjacent one end thereof so thatindividual sample tubes can be placed in the same orientation withinmagazine 14. Those same orienting indicia are used to ensure as wellthat the sample tubes are correctly oriented during desorption ofcontaminants from the collector material for analysis.

In addition to chemical contaminants, the system of this invention isuseful in monitoring air and other gas samples for the presence ofbiological contaminants such as, for example, disease carryingorganisms, spores and viruses. For this use, the collector material 33,34 and 35 may comprise either a trapping substance such as a highefficiency filter, or a biological culture medium that include nutrientsystems for the artificial cultivation of the cells or organisms ofinterest. An air or gas sample is drawn through the media containingsample tube wherein biological contaminants carried in the air streamcontact and are caught by the trapping substance or inoculate theculture media. The sample tube is then transported to a laboratory foranalysis using conventional techniques, including DNA analysis, toidentify the contaminant.

Turning now to FIG. 3, there is shown a preferred embodiment of thesample tube end caps 31. While simple in appearance, the end caps servea number of critical functions in the sampling system of this invention.The end caps must provide a seal for the sample tubes that will preventcontamination of the collector material prior to sampling, but also mustbe easily removed and replaced by automated sample analyzing equipmentincluding, for example, automatic thermal desorbers. During sampletaking, the end caps must seal tightly enough to prevent leakage to thevacuum that is drawn within the sample tube. After a sample has beenobtained, the end caps must seal tightly enough to maintain the samplein isolation, often for extended periods of time, until an analysis isperformed. The end caps also must allow entry of a hollow bore needleduring the sampling procedure. Lastly, the caps must be constructed ofextremely inert materials so that there is essentially no chance ofinteraction between sample constituents and the cap material. For thatreason, it is preferred that all parts of the end cap that come intocontact with the sample be made of or coated with an inert fluorocarbonpolymer such as Teflon® or similar polymers.

Each end cap 31 includes a generally cylindrical cap body 41 having aninternal diameter sized to make a sliding fit over the outside surfaceof tube body 30. A septum 43 closes one end of cap body 41, and issecured in place by means of crimp cap 45 that is anchored to body 41about shoulder 47. Shoulder 47, in turn, is formed by a notch 49 that iscut into cap body 41 adjacent its open end leaving a flange 51 at theopen end of the cap body. A circular groove 53 is cut into the innersurface of cap body 41 to hold and seat O-ring 55 which seals the sampletube when the end cap is in place. The depth of groove 53 determines thepressure that is developed between the O-ring and the tube surface, andso determines the strength and integrity of the seal formed between theend cap and the sample tube. That seal must be sufficiently strong toprevent leakage when a partial vacuum is drawn in the tube duringsampling, but it must not be so strong as to interfere with operation ofanalytical equipment that removes and replaces the end caps on thesample tubes. A groove depth that produces a seal tightness whichrequires about 2 to 3 pounds of force to pull the end cap from the tubeend is about optimum.

An opening is provided in the center of the crimp cap 45 that exposesthe outside central portion 57 of septum 43. Crimp caps suitable for usehere are commercially available, and are routinely used on autosamplervials in gas and liquid chromatography applications. During the samplingprocedure a hollow bore needle is inserted through the exposed septumarea 57 at each tube end. A stream of the gas being sampled entersthrough one of the needles, contacts the collector material 33, 34, 35,and exits through the other needle.

Turning now to FIGS. 4 and 5, there is shown details of sample trappingmodule 12. FIG. 4 shows the trapping module 12 with the front housingpanel removed. Module 12 includes a port 70 into which magazine 14 fits.A plug 72 is provided at the rear of port 70 to provide electricalconnection to memory means that are contained within magazine 14 whenthe magazine is seated in the port. A magazine drive assembly, which isshown generally at 75 and is detailed in FIGS. 9, 10 and 11, is locatedat the bottom of the module below port 70. Drive assembly 75 serves torotate sample tubes carried within magazine 14 to and from a samplingposition by incremental rotation of clutch drive plate 77. Overallcontrol of the trapping module 12 resides in operations module 79 whichincludes a positive displacement pump to draw sample, and controllermeans that commands the operational sequence of the system throughinstructions residing in the memory means 130 (FIG. 6) within magazine14.

A needle drive assembly, shown generally at 80, is arranged to inserthollow bore needles through the exposed septum area 57 at each end of asample tube 16 at the time that tube is indexed at the sampling positionof magazine 14. In a first embodiment, the needle drive assembly insertstwo needles, one at each end, into a capped sample tube. In a second andpreferred embodiment, a pair of upper needles 82,83 are mounted uponupper traveling needle block 85, and a pair of lower needles 87,88 aremounted upon lower traveling needle block 90. In this preferredembodiment, sequential pairs of sample tubes 16 are arranged adjacentone another at the sampling position in alignment with the upper andlower needle pairs.

The upper and lower needle blocks are driven toward and away from eachother by means of a rotating shaft 92 that has opposite lead threads onits upper and lower ends, 94 and 95 respectively. Shaft 92 is powered bya motor and reduction gear box 97 through a gear train 99. The twooppositely threaded ends of shaft 92 engage upper and lower slide blocks101 and 102 which are mounted on guide bar 103 and carry the upper andlower needle blocks 85 and 90. The travel of each of the needle blocksis sufficient to allow clean penetration of the needle tip through thesample tube septum, and in practical terms, is on the order of 1 to 1.5cm. Total travel of the needle blocks Ls limited by switch meanscontrolled by two photo sensors 105 and 106 that are mounted on guidebar 103. A flag mounted on either the upper or lower slide blockinterrupts the photo sensors to produce a signal that stops the motor97.

FIG. 5 shows an end view of the needle drive assembly 80. ConsideringFIG. 5 in association with FIG. 4, the arrangement of motor and gear box97, gear train 99, and guide bar 103 can be more clearly discerned. Astream of gas to be sampled is supplied by way of manifold 108. Arepresentative sample stream is pulled from manifold 108 by way offlexible inlet conduit 110 that is connected to fitting 112 on lowerneedle block 90. A passage within needle block 90 allows closedcommunication between conduit 110 and needles 87 and 88. Conduit 110 isformed as an arcuate loop of large diameter relative to the diameter ofthe conduit so as to minimize bending stresses as needle block 90 movesup and down during the sampling procedure. In similar fashion, a sampleexhaust conduit 112 connects to upper needle block 85 through fitting114 providing a closed path between upper needles 82 and 83 and conduit112. The other end of conduit 112 connects to the suction side of apositive displacement pump, as is shown diagrammatically in FIG. 12.

Structural details of magazine 14 are shown in FIGS. 6 and 7. Referringnow to those Figures, FIG. 6 is a bottom view of magazine 14 with thebottom closure plate removed, while FIG. 7 is an outline side viewshowing the arrangement of sample tubes within the magazine. Magazine 14includes a closed housing that comprises a bottom plate 121, a top plate123, and a side plate 125 extending around the periphery of the housingbetween the top and bottom plates. A connector plug 127 is located onthe rear side plate and is arranged to make mating electrical connectionwith plug 72 when magazine 14 is inserted into port 70. An electronicmemory comprising a printed circuit board containing non-volatile memorychips 130 is located within the magazine. Memory 130 is arranged toaccept and store data from operations module 79 that relate toindividual samples arid, in a preferred embodiment, to use data that isimpressed within that memory to direct operations module 79 in thetaking of samples by the system as will be described in more detaillater.

Rack means are provided within the housing to position and hold aplurality of sample tubes. Those rack means preferably are arranged as arotating magazine carousel that is indicated generally at 133. Carousel133 is arranged centrally within the housing of magazine 14, andincludes a circular upper sample tube holder plate 135 and a lowercircular tube sample holder plate 137. The upper and lower tube holderplates are held in a parallel, spaced apart relationship by a pluralityof posts 139. A rotating block having a circular top flange 141 and acentral bottom post 143 is connected to carousel upper tube holder 135by bolt means 145. Flange 141 slidingly fits within circular recess 147formed on the outer side of top plate 123, and is free to rotate withinthat recess. A driven clutch plate 149 is secured to the bottom of lowertube holder 137 by means of standoff post 150, and is arranged to engageclutch drive plate 77. The carousel is caused to incrementally rotateabout the axis formed by bolt means 145 by a corresponding rotationalmovement of clutch drive plate 77.

A plurality of sample tube accepting slots 153, a total of twenty-fivein the embodiment illustrated, extend inwardly from the circumferenceand toward the center of upper and lower tube holders 135 and 137 as isbest seen in FIG. 6. Each slot in the upper tube holder 135 is orientedto be directly above a corresponding slot in the lower tube holder sothat sample tubes held within the slots are aligned vertically, parallelto each other and to the rotational axis of carousel 133. The width ofslots 153 is set to be slightly larger than is the diameter of tube body30 so that sample tubes freely slide back and forth along the slot. Eachof slots 153 may be sized to hold a single sample tube, or in thepreferred embodiment illustrated in the drawings, are sized toaccommodate two sample tubes per slot. Thus, carousel 133 in theillustrated embodiment has the capacity for holding fifty sample tubes.Slots 153 may be oriented along radial lines, and that arrangement ispreferred when the slots are sized to hold a single tube. When the slots153 are sized to hold two tubes, it is preferred that the slots beoriented at an acute angle 155 to a radius of the top plate so that theinner tube in each slot nests between two adjacent outer tubes. Thatarrangement allows the carousel diameter, and hence the magazine size,to be reduced. Angle 155 may appropriately range between 15° and 45°.

As is best seen in FIG. 7, a circular guide groove 157 is provided inthe bottom side of magazine top plate 123. A corresponding groove 158 isprovided in the top side of magazine bottom plate 121. Grooves 157 and158 form a track in which pairs of sample tubes 16 slidably move. Widthof grooves 157 and 158 is set to accommodate the end caps 31 of thesample tubes 16, while the vertical spacing between grooves 157 and 158is slightly greater that the length of a sample tube 16. Sample tubesare loaded into and removed from magazine 14 through door 170 located onthe magazine side plate, and shown by dashed outline in its openposition. Door 170 pivots about door pin 173, and is biased to theclosed position by a torsion spring 172 that wraps around pin 173.

Carousel 133 is caused to rotate stepwise, one twenty-fifth of arevolution per step, to bring pairs of sample tubes to and away from asampling location. The sampling location is defined by a pair ofsampling ports, 160 and 162, that extend through top plate 123 andbottom plate 121. As a pair of sample tubes is moved into the samplinglocation, the tubes are forced into true alignment with the samplingports 160 and 162 by divider means 163 which has detents 164 and 165machined therein. Outer track spring 167 and inner track spring 168 urgethe end caps of individual sample tubes into the detents thuspositioning the sample tubes in alignment with the sampling ports.Sampling ports 160 and 162 are positioned to be in alignment as wellwith upper needle pair 82,83 and lower needle pair 87,88.

A sample is taken by driving the two needle pairs toward one another byactivating motor 97 until the needle points have penetrated through thesepta 43 that close the sample tube ends. A predetermined volume of gasis drawn through each sample tube, and the needle pairs are then movedapart by reversing motor 97. Carousel 133 is advanced another step, andthe system is then ready to take another pair of samples. That procedurecontinues until sampling is complete, or until all of the sample tubescarried in the magazine have been used.

Individual samples are identified by a number that is assigned accordingthe position of the sample tube within the magazine. Sample tubeposition, in turn, is defined by the rotational position of carousel 133relative to sampling ports 160 and 162, and further by the slot positionof the sample tube; whether it is the inner or the outer tube within thetube slot 153. In a preferred embodiment, the rotational position ofcarousel 133 is determined by a signal generating means that produces adifferent binary signature for each incremental rotational position ofthe carousel. That signal generating means preferably comprises apatterned mask, or encoder plate, 180 of light and dark sectors. Encoderplate 180 forms the outer surface of top flange 141, and is patterned asa series of sectors 181, 182, 183, 184, and 185 that are radiallyarranged in concentric rings. Each sector includes an arc 187 thatsubtends an angle proportional to the incremental rotation of thecarousel from one sampling location to the next. In the magazineembodiment illustrated, which provides for twenty-five sample tubeslots, arc 187 would subtend an angle of 14.4°.

The entire area of each sector is either light or dark. An array ofdetectors 190 (FIG. 4), one for each concentric ring, is located at thetop of magazine port 70. Each detector is arranged to respond toradiation only when a reflective object passes its view, and thedetectors may conveniently comprise an infrared emitting diode and aphototransistor. As may be appreciated from a study of FIG. 8, thesectors making up each radial group may be arranged in a pattern oflight and dark to give each rotational location of the carousel a uniquebinary signature. For example, that radial series of sectors 181, 182,183, 184 and 185 may be assigned the home carousel position, and areflective sector would be positioned below each detector. All detectorswould then respond to the reflected radiation, and the resulting binarysignal would be 11111 (assigning a 1 to a detector responding toradiation, and a 0 to a detector that is not.) Rotation of the carouselin a counter-clockwise direction by one incremental amount would thenproduce a binary signal 11110, and so on. Sample identification dataproduced by detector array 190 is stored in memory 130 along with otherdata that characterizes each particular sample.

FIGS. 9, 10 and 11 present differing views of the magazine carouseldrive assembly, shown generally at 200, with FIG. 9 being a top viewthereof, FIG. 10 a side view, and FIG. 11 a bottom view. Carousel driveassembly 200 functions to rotate carousel 133 in equal increments aboutits axis to present successive pairs of sample tubes 16 into alignmentwith sample ports 160 and 162. Referring now to FIGS. 9, 10 and 11 incombination, assembly 200 includes a drive train support plate 202 whichis pivoted at its rearward end about pivot pins 204 and 205 that aresupported by mounting brackets 206 and 207 respectively. Clutch driveplate 77 is mounted at the forward end of support plate 202, and isbiased upwardly into an engagement position with driven clutch plate 149of carousel 133 by spring means 208. The application of pressure onthumb pad 209 moves plate 202 downwardly which compresses spring 208 anddisengages clutch drive plate 77 from clutch driven plate 149 so thatmagazine 14 may be inserted into or removed from port 70.

A gear motor 210 is mounted at the top rear of support plate 202, anddrives Geneva wheel 212. Motor 210 is started upon command from anexecutive microprocessor 255 (FIG. 13), and is stopped by action oflimit switch 213 after turning Geneva wheel 212 one complete revolution.Geneva wheel 212 is coupled through star wheel 215 and a gear train toincrementally rotate clutch drive plate 77. The gear train includes adriver gear 217 that is direct coupled to star wheel 212, idler gear218, and driven gear 219. Gears 217 and 219 are proportioned such as toprovide the desired incremental angular rotation of clutch drive plate77. In the embodiment illustrated, clutch drive plate 77 rotates exactly{fraction (1/25)}th of a revolution for each full revolution of Genevawheel 212.

Referring now to FIGS. 12 and 13, there is shown in schematic form thefunctions that are broadly incorporated within operations module 79. Agas stream, typically air, is drawn into the system through manifold 108by operation of positive displacement pump 222. Pump 222 is turned onand off by signals 224 from executive microprocessor 255 in response toinstructions 225 provided by electronic memory 130 that is contained inmagazine 14. A mass flow controller 226 may be used to regulate thepumping rate, and also to inform memory 130 of the sample size or massthrough signal connection 228.

In a preferred embodiment, measurements of various environmentalproperties of the ambient air that is being sampled are also monitoredand the data obtained is transmitted to and stored in electronic memory130. Monitored properties may include temperature, relative humidity,and the like. Sensors 233 and 235 may be provided to measure temperatureand relative humidity. Data obtained from sensors 233 and 235 aretransmitted to memory 130 through executive microprocessor 255 by way ofsignal connection means 236 and 238 respectively. The pressure of thesample stream is measured by means of transducer 230, and the valuesobtained are transmitted to microprocessor 255 through signal connection231. Pressure data thus obtained serves as an operational check on thesystem. The sample taking procedure normally operates within definedpressure limits. If the pressure is outside those normal limits itindicates a leak, or a collapsed tube, or an incorrect sample tube, orsome other anomaly.

FIG. 13 is an expanded schematic diagram showing details of therelationship among the various modules making up the sampling andanalysis system of this invention. The heart of the control system isthe executive microprocessor 255 that responds to operating instructionscontained in read only memory (ROM) 256 and random access memory (RAM)257. Microprocessor 255 is provided additional information from a numberof other sources including the rotational position of the carousel fromencoder plate 180, pressure data from transducer 230, and sample takinginstructions from nonvolatile memory 130 that is contained in themagazine 14. As is illustrated in the Figure, data is input into memory130 by means of a programming computer 259 which is located at a baselaboratory. Other data, such as the ambient conditions present duringsample taking and the like, is input into memory 130 from executivemicroprocessor 255. All of that data are then retrieved from memory 130by means of a data collection computer 261, and are collated with theanalytical results from each sample tube to form a single file. Thatprevents mix-up of the sample taking and analytical data.

In carrying out the sampling procedure, with reference to all of theFigures, a binary signal derived from encoder plate 180 informsexecutive microprocessor 255 of the rotational position of carousel 133relative to sample ports 160 and 162 or to another designated homeposition. Microprocessor 255 then activates motor controller 263 whichcauses gear motor 210 to turn Geneva wheel 212 for one completerevolution at which time a signal is transmitted to controller 263 fromlimit switch 213 that stops motor 210. A first sample tube 240 is thenaligned with outer sample port 160, and a second sample tube 242 isaligned with inner sample port 162. Needle motor controller 265 is thenactivated by microprocessor 255 causing the upper and lower needleblocks 85 and 90 to be driven toward one another until upper needle pair82,83 and lower needle pair 87,88 penetrate through the septa that sealthe end caps of sample tubes 240 and 242. Valve 245 is caused to move toits second position upon receiving a signal 246 from microprocessor 255,thus opening a flow path for the gas sample from manifold 108 throughinlet conduit 110, sample tube 240, outlet conduit 114, and secondtwo-position valve 248 to pump inlet line 250, which connects to valve245.

Executive microprocessor 255 then signals pump microprocessor 267 tostart pump 212 and thereby draw a gas volume that is set by instructionsfrom memory 130 through sample tube 240. Valve 245 is then signalled tomove back to the first of its positions, thus stopping flow of gasthrough tube 240. Either immediately thereafter or at some later presettime, second two-position valve 248 is signalled by microprocessor 255to move from its first to its second positions. That isolates sampletube 240, and connects sample tube 242 to pump inlet line 250. Valve 245is then signalled to move to its second position opening up a flow pathfrom manifold 108 to pump 222 through sample tube 242. After a presetvolume of sample is drawn through sample tube 242, valve 245 issignalled to move back to its first position thereby isolating tube 242from the pump. Pump microprocessor 267 is then signaled by executivemicroprocessor 255 to cease operation. The upper and lower needle blocksare again activated, this time to drive the blocks away from each otherand withdraw the needles from the sample tube ends. Microprocessor 255then instructs carousel 133 to incrementally rotate so that another pairof sample tubes is aligned with the sample ports. That procedure isrepeated until the desired number of samples has been taken, or untilall of the sample tubes contained within the magazine have been used.

At that time, the used magazine is removed from port 70, and a newmagazine is inserted. The electronic memory of that new magazine willcontain sampling instructions that may be the same as those contained inthe first magazine, or may be different. In the meantime, the firstmagazine with its used sample tubes is transported to a laboratory foranalysis. Data relating to sample properties is uniquely associated witheach sample tube in the electronic memory 130, and that data isretrieved by the analyzing laboratory as the sample tubes are processed.

It is sometimes useful to take duplicate samples, one for immediateanalysis and the other as an archival sample. Sample trapping module 12may be arranged for duplicate samples to be taken either simultaneouslyor sequentially. In the event that duplicate samples are takensimultaneously, operations module 79 is preferably provided with twopumps 222, and valve 248 is arranged to connect one sorbent tube to eachpump during the sampling operation.

FIG. 14 is a diagram that illustrates a technique for the analysis ofsamples captured by the individual sample tubes. A magazine 14, havingsome or all of its contained sample tubes used for trapping samples, istransported to interface 18. Interface 18 functions to automaticallyremove sample tubes 16 from the magazine 14, one at a time, and load thesample tubes into a desorber 270. The identity of each sample tube andits associated data is maintained by tracking the position of the sampletube in the desorber device relative to its position in the carousel.Desorber 270 serves to quantitatively displace the collectedcontaminants from the collector material 33,34,35 contained within thesample tube. Displacement of the collected contaminants may beaccomplished by means of a solvent extraction in the case of biologicalcontaminants, or by thermal desorption in the case of chemicalcontaminants.

Automatic thermal desorbers for displacing collected contaminants fromsample tubes similar in size and shape to those used in the inventiveprocess are commercially available. One such desorber is sold byPerkin-Elmer Corporation, and is designated its model ATD 400. Thatparticular device, or others similar to it, can readily be adapted foruse in this system. Interface 18 cooperates with desorber 270 to removesample tubes, in order and one at a time, from magazine 14 and then dropthe tubes into the appropriate slot in the desorber carousel. Anelectronic bridge connects interface 18 to desorber 270 to correlateoperations of the two devices and to keep track of and maintain theidentity of the individual samples.

The contaminants that are collected in an individual sample tube aredisplaced from the collector material in desorber 270 by heating thesample tube, and sweeping it with a gas stream to carry the contaminantsfrom the tube into an analytical device 280. Analytical device 280 ispreferably a gas chromatograph, although any other conventionalanalytical techniques such as, for example, mass spectroscopy, liquidchromatography, capillary zone electrophoresis, infrared spectroscopy,and the like may find use. When using gas chromatography, a detector isselected that is appropriate to the kind and concentration ofcontaminants of interest. Examples of suitable detector systems includethermal conductivity detectors, flame ionization detectors, massselective detectors, photoionization detectors, ultraviolet detectors,and other specialized detection systems.

It can be appreciated that the described invention provides a uniquesystem to collect and to archive samples using solid state technology.Samples may be collected over a period of time that can range fromminutes to hours per sample. That permits the characterization of theair or gas stream being sampled to determine virtually all contaminantsthat were present during the period in which sampling was conducted.

The embodiments of this invention in which exclusive rights are assertedare set out in the following claims.

We claim:
 1. A gas sampling system comprising: a plurality of sampletubes, each said tube containing a solid collector material, the ends ofeach said tube having a vacuum tight end closure, each said end closurehaving a pierceable septum; a magazine arranged to store said pluralityof sample tubes and having means to sequentially move individual sampletubes into and out of a sampling location; and a sample trapping modulehaving a port arranged to accept entry of said magazine, said porthaving means to make mechanical and electrical connection with saidmagazine when the magazine is seated in the port, said trapping modulehaving a pair of hollow bore needles spaced apart on the same axis, thepoints of said needles facing each other, the needles arranged to moveback and forth along said axis, and to penetrate through and withdrawfrom the end cap septa of a sample tube when said tube is at saidsampling location.
 2. The gas sampling system of claim 1 wherein thesolid collector material contained in said sample tubes is selected totrap chemical contaminants that are contained in the gas being sampled.3. The gas sampling system of claim 2 wherein said collector material isan adsorbent.
 4. The gas sampling system of claim 1 wherein the solidcollector material Contained in said sample tubes traps biologicalcontaminants that are contained in the gas being sampled.
 5. The gassampling system of claim 4 wherein said collector material is a highefficiency filter.
 6. The gas sampling system of claim 4 wherein saidcollector material is a culture medium.
 7. The gas sampling system ofclaim 1 wherein said magazine includes non-volatile memory meansarranged to transmit, to receive, and to store data, said stored dataincluding instructions that direct and control said sample trappingmodule.
 8. The gas sampling system of claim 7 wherein said instructionsinclude the volume of the sample to be taken.
 9. The gas sampling systemof claim 7 wherein the data that is received and stored by saidnon-volatile memory comprises sampling data including temperature andpressure of the gas being sampled and total sample volume.
 10. The gassampling system of claim 1 wherein said magazine comprises a circularcarousel that is incrementally rotatable around a central axis and isenclosed within a housing, said carousel having means to accept and holda plurality of sample tubes arranged in a circle about itscircumference.
 11. The gas sampling system of claim 10 wherein saidmeans to accept and hold a plurality of sample tubes comprises an upperand a lower sample tube holding plate, both said plates having aplurality of superimposed, equi-spaced, sample tube holding slotsextending inwardly from the plate circumference toward the platecenters.
 12. The gas sampling system of claim 11 wherein said tubeholding slots are extended deeply enough for each slot to hold twosample tubes, wherein the two tubes in a slot are simultaneouslypresented at said sampling location, and wherein said trapping moduleincludes a second pair of hollow bore needles disposed parallel to saidfirst needle pair, the two needle pairs arranged to simultaneouslypenetrate the end cap septa of the two sample tubes within a singleslot.
 13. The gas sampling system of claim 11 wherein said slots areoriented at an acute angle to a radius of said sample tube holdingplates so that the inner tube in each slot nests between two adjacentouter tubes.
 14. The gas sampling system of claim 11 wherein eachincremental rotation of said carousel is equal to the arc subtendedbetween adjacent tube holding slots, and wherein said carousel includesa signal generating means that produces a different binary signal foreach rotational position of said carousel.
 15. The gas sampling systemof claim 11 further including an interface means that is arranged toremove sample tubes from said carousel, one at a time, and load saidtubes into a contaminant desorbing and analysis means.
 16. The gassampling system of claim 15 wherein said interface means maintainssample identity by tracking the position of each sample tube loaded intosaid desorbing and analysis means relative to the carousel position ofthat same sample tube.